The present invention relates generally to an improved floral display foam block, and more specifically to a floral foam display block prepared from frothed urea-formaldehyde resin. The urea-formaldehyde resin is treated so as to render the resultant foam hydrophilic in nature, and further providing for extended lifetime of cut flowers retained therein.
Urea-formaldehyde foam is a desired material for retention of floral displays, and has been widely utilized for such purposes in the past. Normally, however, urea-formaldehyde foam is hydrophobic upon curing, and may contain more than about 60% of closed cells in the foamed structure. The foam may be rendered substantially open cell by mechanically or physically crushing.
In the past, attempts have been made to render urea-formaldehyde foams hydrophilic through the soaking of a cured foam in an aqueous solution of a surfactant. However, it has been found that most surfactants, particularly those of the alkyl-aryl sulfonate type do not render the resultant cured foam product hydrophilic, inasmuch as the hydrophilic ends of the surfactant appear linked, bonded, or otherwise attached to the inside surfaces of the cured resin material. Furthermore, the use of alkyl-aryl sulfonates renders the moisture content of the foam generally anionic in nature.
It has been found that when the water content of a saturated floral display foam block is reasonably anionic, the water and the structure becomes toxic to cut flowers retained therewithin. While the reason for the toxicity is not precisely known, it appears to be due to the presence of toxic soluble salt levels, or toxic burning of the cut stems, thus generally prohibiting natural pathogens of the cut flowers to function efficiently or normally, and furthermore by not allowing the natural function of plant enzymes which regulate plant metabolism to function normally. Tests have verified that the quality of cut flowers deteriorates rather rapidly under these conditions. Evidence of the deterioration includes darkening of the stems, the drying of leaves, and the drooping of the flowers prematurely.
It has been found that the ionic balance of the foam may be adjusted by post-cure treatment of the foam with an equivalent cationic surfactant so as to control the ionic balance of the water. The alkyl-aryl sulfonate solutions are counter-balanced with an equivalent molar presence of quaternary ammonium salts, thus contributing to a double-decomposition of the alkyl-aryl sulfonates and quaternary ammonium salts through precipitation of an insoluble residual salt. As a result, the toxicity level of the foam is reduced, while the hydrophilic nature of the foam is preserved. The lifetime of cut flowers retained within the floral display foam increases, and exceeds that of the same cut flowers in water.
As a further feature of the invention, the pH of the foam is controlled to be at a desirable level, specifically in the range of approximately 3.5 to 4. Generally, urea-formaldehyde foams may have a pH of less than 2, which is normally the pH upon initial setting of the foam. Cured foam utilizing alkyl-aryl sulfonate stabilizers exhibit a pH of about 3.5 to 4.